This application relates to a method of attaching lids or caps to jars to insure that seals are properly made.
In the prior art, food products are often packaged in glass jars. Caps tightened onto jars often have an aluminum seal received within the cap. An outer face of the aluminum seal contains an adhesive, and the cap is screwed onto the jar. The cap and glass jar are heated together to melt the adhesive, and seal the aluminum seal on the jar.
Applicant has found this method somewhat unsatisfactory. An undesirably high percentage of the aluminum seals do not properly seal. This is particularly true when the jar is glass, and the cap is plastic. It is believed the various coefficients of expansion in a heated glass jar, the aluminum foil, and the plastic cap, allow relative creeping therebetween which results in an ineffective or improper seal between the cap and the glass jar. When a cold cap with an inner foil membrane has been sealed in an induction sealer onto a container the caps have a tendency to back off and has to be re-torqued. Applicant has developed a system or method to reduce the amount of creepage between the three materials.
In the present invention, the cap is heated prior to being placed on the jar. The jar is left unheated as the cap is attached. The cap and jar are then heated to seal the aluminum. Applicant has found that such a method results in a very high percentage of jars receiving a proper seal.